Converting '96 B2500 from 3sp. to 4sp. A/T?

Hey all,
I have a co-worker that bought a '96 B2500 van with the 3.9 and 3 speed automatic (32RE?) tranny, and he was wondering how difficult, if at all possible, it would be to convert it to a 4 speed overdrive tranny. The 42RE should have been offered in this year if I'm not mistaken, but what would be involved in the conversion? How is the overdrive controlled? Thru the PCM, or is there a seperate TCM? Would a simple re-flash make it work once all the necessary wiring was done?
Also, since Chrysler tends to be rather generic with their wiring harnesses, is there a possibility that the wiring for the overdrive tranny would be there already and just not plugged in?
He's an ASE certified technician, so doing the conversion itself, and even changing out a wiring harness wouldn't be that big of a deal, but since he's kind of a newbie in the world of Chrysler products (he was a GM tech for many years at a new Olds/Pontiac store), he doesn't really know what makes them tick in very intricate detail.
His questions are beyond what I know about things too, so that's why I figured I'd post here and see if maybe someone knows what would need to be done.

Thanks for any help you can give us!

-Mike

The trans. that's in the van now is a 32RH which is a hydraulic 3spd. auto with electronic lockup torque converter controlled by the PCM.

'96 was the first year for the 46RE, which is an electronic controlled 4spd. I'm not totally sure this transmission was offered on a V6. The problem I see is that you'd have to swap in the proper harness for the electronics on the transmission. This would more than likely have to be a V8 harness and it wouldn't plug into your PCM. My suggestion would be to find a pre-'96 42RH transmission, which is hydraulic controlled and was offered on V6 vans.

Well heck, that would be a lot easier than messing around with a 46RE! From what I remember reading, all that would need to be done then to get the O/D working would be to install the switch in the dash, and run power to it and hook the wiring up to the transmission correctly. So basically, my "to get" list would be a pre-'96 46RH (or 44RH?) tranny, O/D cancel switch, and the correct driveshaft out of that same vintage van with that tranny and same wheelbase?

My co-worker commented today that he's getting 15.6 MPG in mixed driving. For what it is, I can't see that as being too horrible. I don't think it will get too much better with O/D than it is right now, do you?

My '94 get around 16-18mpg on OD with a V8.

No such beast as a 44RH...there's a 42RH for the 3.9 and a 46RH for the 5.2 & 5.9. The 46RH will bolt up to the 3.9 though.

Yes you will need a driveshaft...the OD transmission is a bit longer.

That was a typo that I didn't catch...Probably as I was sitting there with a sneezing fit and trying to type at the same time! You got the point though!

The DW's 2000 primetime conversion van V6, 3.9L, gets 14 city and 18 highway. It's the B1500 in the sig. No OD either. A good tune up and the tires inflated to 50psi that is the norm should do it. Are the injectors dirty???

this was one of my questions.

how did the conversion go? did he go thru with it?

i have the same prob with my '96 B1500 with the 3.9L/3 spd auto. if i don't granny it, i get 13mpg in the city and 14-15mpg on the highway. if i granny it, and with no a/c, i'll just barely break 16mpg.

other plans to improve my mpg are a Black Magic Flex-a-lite Electric Fan (NIB, was for my Mustang) and the Chrysler SRT 10 crank pulley (bigger than the Asp UD pulley, but smaller than the factory pulley on the 3.9L). these 2 mods would require the 136 amp alt upgrade that originally was an option for my van.

off course, i also want to upgrade the gears outback, the factory 3.21's, to 3.55's, and that'll probably kill any mpg increase i gained from the above upgrades.

Originally Posted by QQB825

off course, i also want to upgrade the gears outback, the factory 3.21's, to 3.55's, and that'll probably kill any mpg increase i gained from the above upgrades.

Yeah but won't that be a nice little overall improvement? Gain a nice boost in acceleration and towing competence without a penalty at the pump. And you may see an improvement in highway mileage after all compared to a three-speed auto.

It's really tough to compare mileage between vehicles, though, on a forum. Just a difference in terrain will make a large difference in gas mileage, not to mention driver habits.

Originally Posted by Intrepidacious

Yeah but won't that be a nice little overall improvement? Gain a nice boost in acceleration and towing competence without a penalty at the pump. And you may see an improvement in highway mileage after all compared to a three-speed auto.

yeah, hence the 3.55 swap in the near future.

i've heard some ppl see the increase in mpg, i'm hoping i'm one of them.

Originally Posted by Intrepidacious

It's really tough to compare mileage between vehicles, though, on a forum. Just a difference in terrain will make a large difference in gas mileage, not to mention driver habits.

oh, absolutely. on vacation last month, i took the costal route down to NC and had the best gas milage ever, 18.5 mpg. coming home, i took the inland route (over the mountains) and barely broke 17 mpg. both way i drove with the cruise on 70-73 mph.

I've been considering switching over to a 3.92 ratio with anti-spin. I now have 3.54 ratio. But I figure with OD transmission I shouldn't lose that much mileage....if any.

I bet you're right -- I haven't done the math but I bet the overall ratio won't be worse. If third gear was 1:1 on a three-speed, and fourth is somewhere in the vicinity of .70:1 to .75:1, that'd give a lot of room for a more aggressive rear axle ratio.

In fact, you'd probably be very disappointed if you didn't change the rear-end ratio, as fourth gear may be too tall for anything but nice flat terrain.

Originally Posted by Dodgevanman

My '94 get around 16-18mpg on OD with a V8.

No such beast as a 44RH...there's a 42RH for the 3.9 and a 46RH for the 5.2 & 5.9. The 46RH will bolt up to the 3.9 though.

Yes you will need a driveshaft...the OD transmission is a bit longer.

bump!

do you know the years Chrysler used the 42RH & 46RH?

I wanna say around 88 or so to 95. 96 started the "RE" transmissions.

Originally Posted by Dodgevanman

I wanna say around 88 or so to 95. 96 started the "RE" transmissions.

thanks. my cousin just got in an 80's van with a new rebuilt trans. i may have found what i need.

Answers to a few questions.
The 42rh was started production in '88, the 46rh in '90.
The 42rhwas used behind 318's in some vans '88 - ?
The driveshaft from the swap van needs to have the same type rear axle because the U-joint to axle center is different on some axles... check this dimension.
Some 904 series (32rh) have lock-up convertors.
Also look for a 90* speedometer cable adaptor... since the transmission is longer. Some late 80's models have this.
Most important is to get the larger diameter cooling tubes and fittings so the transmission will survive.
The OD ratio is 0.69 to 1
The 44rh transmission was used on 4.0l jeeps.
Lastly you will need a kit with pressure switches (to control lockup and OD upshift) and a vacumn or throttle switch to override this function... Lookup how to swap a 518 transmission on the net and you should find info.
Sorry to talk so long but I'm doing the same to mine so I have done a lot of reseach on the subject.
--B-300--

this is great info, thanks.

A quicky question as I'm reading your posts. I have a 95 B2500 with a 46RH tranny. Can someone tell me what diameter lines go to the transmission cooler. Thanks.

Originally Posted by Dodgevanman

The trans. that's in the van now is a 32RH which is a hydraulic 3spd. auto with electronic lockup torque converter controlled by the PCM.

'96 was the first year for the 46RE, which is an electronic controlled 4spd. I'm not totally sure this transmission was offered on a V6. The problem I see is that you'd have to swap in the proper harness for the electronics on the transmission. This would more than likely have to be a V8 harness and it wouldn't plug into your PCM. My suggestion would be to find a pre-'96 42RH transmission, which is hydraulic controlled and was offered on V6 vans.

bump.


a few more questions. is the 46RE controlled by the PCM? if one had a complete donor van (5.2L/46RE), and swapped everything that is necessary over (trans, driveshaft, cross member, harness(es), sensors, re-pinned the PCM plug, etc.), would a 3.9L PCM be able to properly control the 46RE?

Both the "re" and "rh" versions of the transmission are controled by the PCM.
The rh transmission uses a hydraulic governer to control the 1st-2nd-3rd shifting and the PCM to control OD and lockup functions using inputs from the vehicle speed sensor, coolant temp, throttle position sensor and map sensor if the tps fails.
The re transmission has a speed sensor ahead of the OD unit and a pressure transducer and duty cycle solenoid to produce governer pressure that can be modified by the PCM depending on temp and tps. By doing this the re transmission can be made to shift similar whether hot or cold for smoother predictable shifting. The OD and lockup are controled similar to the rh transmission
I don't believe a 5.2 PCM will work on a 3.9 engine..It's a 8 cylinder vs. 6 cylinder problem. Why not use the 5.2 engine also?
--B-300--

my mechanic pulled in a running '96 USPS cargo van with a 5.2L/4 spd. the trans has 20k on it; but the engine has 350k on it. it runs, but i'd want to do a total rebuild on the 5.2L, and i didn't want to spend that cash. we'll see. maybe i'll trade it all for a '95 46RH.